The original Apple Pencil was released along with the original iPad Pro in September 2015. The Apple Pencil can be used by the iPad Air (Generation 3), iPad mini (Generation 5), iPad Pro 10.5-inch, iPad (Generation 6 and 7), iPad Pro 12.9-inch (Generation 1 and 2), and iPad Pro 9.7-inch. It pairs to an iPad device using Bluetooth, and has a removable magnetically attached cap hiding a Lightning connector.
The original Apple Pencil somewhat awkwardly charges by plugging it into the lightning port of an Apple device; however, it also includes a female-to-female adapter that allows charging with a Lightning cable. While a full charge can last up to 12 hours, a 15-second charge provides about 30 minutes of use.
The Apple Pencil can be used for writing, drawing, or annotating in a wide variety of apps. Apple describes its features as having “pixel-perfect precision, tilt and pressure sensitivity, and imperceptible lag.”
Source: Wikipedia, Apple (description, specifications)